if u`d luv t save it for last then find water soluble coloring of ur choice and soak it 2 hours - providing if the tshirt has 1 color in general..... , particularly if the diminishing colors is in the figuring forms or need a special attentions on wording or pic, u hav t repaint it and redraw accordingly with reapplying its own generic colors/ use color for fabrics etc...,....  then after dried off... again soak it again with sodium silicate/color fixer overnight, rinse wash.... color will stay..... happy testing!